Bill Cheek - World Scanner Report

Publisher/Editor: M. D. Cheek. Sr. aka "Hr. Riaoraortis

V1N4: April, 1991

THE WORLD SCANNER REPORT
A Journal of VHF-UHF Scanner Technology t Engineering

Published at: CQHHtronics Engineering; PO BOX 262473; San Diego,

SCANNER MODIFICATION HANDBOOK VOL-2 RELEASED

It's been a long time cosing but Vol-2 oP ay Scanner HodiPication
Handbook is now available Pros the publisher, other sail order
Piras and directly Proa ae. I think the price is about the saae
everywhere, but autographed copies are available ONLY Proa ae.
Price and ordering inPoraation are included in the brochure with
this issue and on the blank on Page 7. IP you’d like a special
greeting or salutation on your autographed copy, just ask. And
now let's do a brief suaaary, thouqh reviews are in this aonth’s
"POPULAR COMMUNICATIONS" and MONITQRINS TIMES aagazines. I’a sure
Vol-2 will be objectively reviewed in other publications as well,
so Poliowing is aore oP a synopsis oP the contents than a review.

I don’t toot ay own horn all that well, begging your pardon.

Vol-2 with its 220 pages is 40 pages larger than Vol-1. There's
not as aany new aods as in Vol-1, but there are aore sophisticated
ones, aore projects and aore helpPul hints in addition to lots oP
general inPoraation on the science and art oP scanning. How here
is a suaaary oP what you'll Pind in Vol-2:

+ Introduction to aodiPying your scanner
+ Using a VCR to record scanner action
+ Special techniques Por welded PRQ-34's
^lected troubleshooting procedures Por the PRG-2004/5/6
i . . eaapliPiers Por scanners
f Coaputer Bulletin Boards and Scanning
+ QPficial Prequency allocations, 25 MHz - 2200 MHz
+ Historical list oP scanners; list oP over 200 scanners
+ Buying used scanners

+ Trunked radio systeas; how the aajor ones work
+ Alignaent instructions Por the PRQ-2004/5/4; (with basic tools)

+ Build your own Pixed +5v and variable DC power supplies
+ More audio output Proa your handheld scanners (several ways)

+ Telephone Dial Tone Decoder; gives the digits oP dial tones!

+ Review & update oP Vol-1 's modifications; errors, new ideas
+ A great new Analog S-Heter; (really great!)

+ Digital (LED) S-Meters; two types; either is great!

+ Analog & Digital (LED) Center Tuning Meters; shows +1259 Hz!

+ Keyboard Memory Block Controller Por HDDs 16/19; no switches!

+ Extended Delay, 0-12 sec; you adjust to suit!

+ Add an Event Counter to your scanner; counts t oP transaissions!

+ CTCSS Tone Decoders Por scanners; (also a "tone tinder 11 !)

+ Carrier-On-Indicator Por scanners; shows Squelch breaks
+ Hew Automatic Tape Recorder Switch; easier than HDD-6
+ Shielding equipment with plastic cases; stops soae RFI
+ Cellular restoration, PRO-2022; easy
+ Speeding up the PRO-2022; easy
+ 3,200 channels Por the PRO-2022; just like the PRO-34
t^eeding up the PRO-34; three approaches
v ;rease the battery power oP the BC-100 Si 200XLT ; several ways
+ Cellular restoration Por later BC-200/205XLT; new procedure
+ Speeding up the BC-20B/205XLT ; double or better
+ Cellular restoration Por later BC-760/958XLT; new procedure

CA 92196 Copyright (c) 1991 <A11 Rights Reserved) $4.30

Many oP the aods in Vol-2 are geared to the PRO-2004/5/6 but can
be adapted to other scanners with minimal or varying degrees oP
diPPiculty. In the coming months, I will try to show here in the
'HSR' how to adapt soae of the aods Por other scanners. This
cannot be done upon request on an individual basis because a lot
oP expensive R Si D is required to tailor a set oP procedures Por a
speciPic scanner, fly books couldn't do that Por thea all but the
'HSR* will try it Por the aore popular radios, one at a tiae.

Vol-2 continues with the tradition of exceptional detail on all
the projects and aods so that the casual hobbyist will be capable
oP doing aost oP thea iP he/she can read and Pollow directions. I
ai still entertained by the conent of a reviewer in the ‘US
SCARRER REUS' last year Mho said that ny aods in Vol-1 Mere so
hairy that even he, a technician, n ouldn't try thea. Yet, I have
had Peedback Proa soae 1,000 lay readers who prodaiaed success,
iP not at Pirst, then shortly thereaPter with a little help. That
tradition will continue with assurances oP ay help Por little aore
than the cost oP a BASE and a loose extra staap along with your
letter oP description and inquiry.

Vol-2 includes updated Cellular Restoration procedures Por the
newer BC-200/205XLT and BC-760/950XLT rigs. Seems there are two
production versions oP these units, and each requires a slightly
diPPerent procedure, depending on the age oP the units. When I
learned oP the production changes, Vol-1 had already gone to press
and it was too late to make the changes. This is one reason why
the 'HSR* was born. You'll always get the latest scoop on any new
inPoraation that impacts the contents oP ay books.

There are a Pew typo errors throughout Vol-2, but nothing as
serious as in Vol-1. Thus Par, no errors in the technical side oP
the book have turned up, and are not likely to since I have used
the schematics and the book's technical material extensively
without problems since writing it last summer. On the whole, I
think Voi-2 is a natural shelP-aate Por Vol-1, and initial
reaction Prom its readers is exceptionally positive. I'll leave
it now to the reviewers and to YOU to judge the merits oP Vol-2.

FROM FIDONET'S COMPUTER BULLETIN BOARDS

EDITOR’S NOTE: By and large, I Mill reprint selected a essages
froa coaputer bulletin boards without editing thea other than to
econoaize on space. For exaaple, the spelling and graaaatical
errors in the below message are the author's ; not nine. Editorial
license is a great responsibility and « hen 1 guoie others' Morks,
their errors w ill usually be guoted verbaiia. Rho a a 1 to change
soaeone's meaning? Just he aware that the chatter to be found on
the coaputer bulletin boards is not always authoritative, and aore
often than not, only represents one writer's opinion. As I guoie
these messages froa tiae to tiae , you should draw your own
conclusions. The expressed opinions Kill not always he mine. /B C

- please turn to page 2 -

ANOTHER OPINION OF APR SCANNERS

Public Message (Sent)

Message « 8795 *SHQRT-WAVE*

To : Fred Hatfield
From : Hank Lane
Subject : ACE AND AOR SCANNERS
Date : 91/02/25 l:s3:0B

For anyones info, here is ay story on ACE and AOR. I bought the
AR100B from Srove and rcv'd it on Friday Aug. 31, 1998. Immediate
probs were poor senesittivity and birdie obliteration 154-155 MHz.
I returned trie unit to ACE (Srove doesn't service! on Sat. Sept,
1, 1998 for repairs. I continued to call Ace every couple of weeks
for 4 months for updates on repairs. Their standard answer was
that they hac “not received the documentation' yet to allow the
birdie to be fixed. Being fed up, I called ACE on Dan. 18, 1991
and asked for my money back. ACE said “no can do“, but they

promised to send a new , working AR1B0B right away. One week

later- still no scanner. I called Bob Srove and explained the
whole problem. Although his return policy time period had long
since expired, he said he would help to resolve the issue with
ACE. To make a long story short, 6rove talked with ACE and I
finally got my money back; from Srove, not ACE who still has my
scanner. Lessons from this; 1! Natch out for AOR handhelds. This
is my second reject of one of their units. 2) Natch out for ACE.
This is my first direct experience with them (and probably ay
last) . 3) Three cheers for Srove Enterprises. I’ve dealt with

them since their start and have had nothing but outstanding

service and products (AOR handhelds excluded! and excellent prices
and delivery. 4! I still have $480-508 to invest for a good
all-band scanner. .....still waiting for one to appear.

TBBS V2.1/NM Origin: ANARC BBS (913)345-1978 (280/3!

EDITOR'S NOTE: If and when I encounter good things said about ACE
Conunications arid AOR scanners, ! w ill print the i also. Please
direct ae to any sources of such if you knots of any. IRC

A NEW HANDHELD SCANNER FROM RADIO SHACK??

Public Message (Sent)

Message * 4177 *SHQRT-HAVE*

To : All
Fros : Paul Lukas
Subject : Realistic PRO-35
Date : 91/83/25 16:46:88

Here s the specs for the new Realistic PRD-35 scanner:
Channels: 280

Banks:

10 (28 channels each)

Scan:

25 channels/second

Display:

10 digit backlit

Priority:

1 channel

Delay:

Yes

Lockout:

Yes

Search:

Yes

Monitor Ch:

Yes (10?)

Dimensions:

Same as PRO-34

Power:

6 "AA“ batteries.

Mem Backup:

Capacitor, 1 hour

Connectors:

BNC antenna, earphone, DC power, DC charge

Freq Range: 30- 50 MHz

106-174 MH:

220-512 MHz (Military air, AM mode??)

806-B23 MHz
851-868 MHz
896-999 MHz

This doesn't look a whole lot different than the PRO-34 (but I'm
guessing that we can't enable cellular on this one!).

SuickBBS 2.66/0 (Eval)

♦Or i gi n : < MUFQNET-BBS Network) Memphis TN: 981-785-4943 (1:123/26!

EDITOR'S NOTE: interesting ihat the PSO-34 went on sale a few

nonths ago for U99 and again just this week for f 239. It nould
then seen that a replacenent is on the way. I can't vouch for the
above nessage, but the writer seens to know something. If true,
look for the PRO-35 to arrive in late April or early hay.

A READER WRITES... ■ “My younger brother recently purchased an
AOR-100B handheld scanner. He kept it less than a week. Problems
were as follows: very difficult to program and use; had to use

the 18 db attenuator with an outdoor antenna. Even in this low
population area, it was very susceptible to noise and adjacent
frequencies, and had poor quality sound. He both used Uniden
Bearcat BC 280 XLTs for comparison. He both feel there is no
comparison. The Uniden is the far better scanner. Still the
extra frequency range of the AR-1B0B is something we both desire.
Thought you might appreciate this input.’ Don L. Engles (Frosty).

A NIFTY LITTLE TIP., from a correspondent suggests the use of an
LED wired across the terminals of each extension speaker used
multi-scanner monitoring station. Seems there might be times when
it is difficult to tell from which speaker (and scanner) a given
signal is coming. The LED blinking in synchronization with a
voice will let you know instantly which speaker and scanner is the
source. I was a little concerned about this scheme at first,
until I tried it. The volume of the scanner has to be turned up
pretty strong to make the LED flash noticeably but it does work
without any apparent ill effect. Some LEDs are more sensitive
than others, so you might do well to try several types and sizes
and select the one that flashes with the least amount of volume.
An alternative is to deploy MOD-32, the Carrier On Indicator given
in Vol-2 of my Scanner Modification Handbook .

A POTENT SQUELCH MOD FOR THE PRO-2004 & 2085

(and other scanners)

By “PROFESSOR PEABODY"

EDITOR'S NOTE: This » onth ’ Professor Peabody’ takes us into an
area of the scanner that is tost conton in all scanners, the
HFH-Osc-hixer-lF-DeioduIator chip. Hhile name, part i and the
number of pins of this chip may differ fro m one scanner to
another , they're all essentially the sane and they work in the
same way. For several years, Radio Shack scanners have used the
U-li42§ chip nhich is w hat the Professor refers to below. This
same chip or an equivalent is used in lost other modern sea nr,
sc the Professor's Squelch hod light uork in lots of oinr,
scanners besides virtually all Realistic scanners. This chip
figures into a lot of our modifications, past, present and future,
so 1 am including in this issue some data sheets for the three
types of chip in common use. The 16-pin HC-3357 is a spitti n'

THE HURLS SCAHHER REPORT’ (c) 1991

V1H4 - Page 2

itage of the TK-18428 and the SC-335? in either the 18-pin or the
28-pin versions, closely resettles the chips used in Ilniden and
Regency scanners. The tain difference along the three is the
nut her of pins; 16, 18 or 28. Just cotpare the chip's Functional
Stock Biagrats and the nutter of pins shorn in the Bata Sheets on
6 with the chip data given in your scanner's Service Hanual,
and then apply the belon intonation:

Greetings Fellow Hackers: This aonth I would like to turn you on
to a aod that was inspired by your huable editor of "NORLB SCANNER
REPORT " in V1N2. Bill Cheek discovered that the Radio Shack
Pro-2006 has a new electronic switch in the Squelch circuit of
IC2, the TK-10420 chip. This is a CNOS switch chip (IC-1B) wired
in series with R-152 133k) between pins 12 and 14 of IC2. Owners
of the PRO-2004 and PRO-2005, which use the saae NFH chip, can
refer to the PRO-2006 Service Hanual if details of this new
circuit are needed. You PRO-2006 owners just sit tight this aonth
since we're going to aake other scanners sore like yours.

The standard “Squelch Hod’ (HOD-4) for the PRO-2004, 2005 and aany
other scanners has been to either reaove the Squelch-Hute resistor
altogether or add aore resistance between the SQUELCH and HUTE
pins of the NFH-Qsc-Hixer-IF-Deaodulator chip; usually a TK-10420
but which also can be an HC-3361, HC-3359, HC-3357 or either an
NJH-3359D-A or TK-10421 in Uniden scanners. This aod allows a
tighter squelch action to open and close the receiver audio
circuits. As soae of you have experienced, it works but it seeas
to always needs adjustaent depending on how noisy the airwaves
are. Soaetiaes a tight squelch works quite nicely. Other tiaes a
loose or original Squelch action is required so the radio doesn't
v ~ ■* up on every ataospheric burp. A near-perfect Squelch action
discovered with an unheralded new change in the PRO-2006.

The new electronic switch, easily added to aany scanners, actually
coabines the desired tight squelch to trigger on weak signals, but
switches in a resistor (22k-47k) to loosen the Squelch for when
signals are present to stop the chopping of the audio that sight
happen on weak signals. I installed a circuit siailar to the
PRO-2006'5 in ay PRO-2005 by using one section of a 74HC4066 quad
bilateral switch. The aore coaaon CD-4066 can also be used to
perfora this bit of Squelch aagic. Either of these 4066 chips
have four switches on the chip and we need only one, so three
"spares" will be available for other projects sosetiae. See the
scheaatic elsewhere in this issue for the gory details.

A control pin of the 4066 chip should be connected to the
receiver's "HUTE" function pin at the CPU/sicroprocessor. One
lead of the stock resistor between the Squelch and Hute pins of
the TK-10420 (or equiv! chip is cut, and the two loose leads are

then wired to the Input 4 Output pins of the new 4066 chip (which

doesn't aatter). Two other wires to/fro» the 4066 chip are

required; one to ground and one to the scanner's +5v. That’s the

extent of the necessary effort. External controls not required.

NOTE: I will refer to two different HUTE pins in this article;
one. is the HUTE pin on the CPU/aicroprocessor chip, and the other
,e Audio Hute pin on the NFH—Qsc-Hixer-IF-Deaodulator chip,
which is the aain subject chip of this article. Don't confuse the
two "Hutes". They're different pins on two different chips, ok?

When the scanner is scanning or searching, the HUTE signal at the
CPU/fli coprocessor is low or zero volts and turns the 4066 switch
off which puts an infinite ispedance between the TK-1042B (or
equiv) chip's Squelch and Hute pins 12 5 14. This gives the
desired "tight" Squelch action for weak signals. Now when the
receiver senses a signal and unsquelches, the CPU's HUTE signal
goes high at about +5 volts or so. This turns the 4066 switch ON
which connects the stock resistor back in circuit to loosen the
Squelch so that it doesn't release before it is supposed to. I
hops I'a not boring you with too auch detail but the operation has
to be explained in order to check for proper operation.

I have installed this "new" squelch aod and tested it for a weetc
now. I like it auch better than the original Squelch Hod. I get
the saae triggering sensitivity as before but without the chopping
that drove ae crazy. I even reaoved the 100K pot used for the
original HQD-4 adjustaent of the Squelcn action and used the hole
for another aod. So, now the squelch action is autoaatic and
neat. Of course, if you still like the original Hod you can
insert or keep a 100k-200k pot in series with the resistor and the
4066 switch and have it both ways. Try it and see if you like it.
The guys who awn a PRO-2006 probably didn't realize anything was
different but the PRO-2004, PRO-2005 and other scanners will see a
substantial difference in the Squelch action, for the better)

Here's a table that shows the different types of chips and
associated resistors to clip for the installation of the new
Squelch Nod in different scanners:

SCANNER

CHIP
Ckt SYH

CHIP No.

RESISTOR

COHHENTS

PRO-2005

IC-2

TK-10420

R-152 (33k)

PRO-2004

IC-2

TK-10420

R-148 (47k)

PRO-2003

IC-104

HC-3357P

R-222 (22k)

PRO-2002

IC-101

HC-3357P

R-197 (47k)

PRO-2024

IC-2

HC-3361N

R-76 (33k i

Siailar to HC-3357

PRO-2022

IC-1

HC-3361N

R-91 (33k)

Siailar to HC-3357

PRO-2021

IC-2

TK-10420

R-64 (27k!

PRO-2020

IC-101

HC-3357P

R-199 (39k)

PRO-34

IC-101

TK-10420

R-162 (27k)

PRO-32

IC-101

TK-10420

R-163 (27k!

PRO-31

IC-1

TK-10420

R-46 (22k)

BC-200/205

IC-401

TK-10421H-2

none

See Notes 4 1

BC-400/560

IC-1

NJH-3359D-4

none

See Notes 4 2

BC-760/958

IC-2

NJH-3359D-4

none

See Notes 4 3

NOTES: Recent Bearcat scanners are a little different from the
Realistics, and we don't know if the above Squelch Hodification
will perfore the intended purpose. This is largely because the
Audio Hute pin on the NFH chip is not used in the Bearcats. This
aeans that there is a full-tiae high iapedance between the Squelch
Input pin and the Audio Hute pin. It should be not be difficult
to install the 4066 Squelch Switch contacts and a series resistor
between the unused Audio Hute pin and the Squelch Input pin.
Refer to the specific notes below:

1. BC-200/205 and Regency R-4030 : Pins 15 and 17 are the

pertinent pins, with 17 not used. The control pin of the 4066
switch should go to the CPU, IC-201, Hute pin 58, or either

THE NORLD SCANNER REPORT ' (c) 1991

lflN4 - Page 3

side of R-241 , whichever is aost convenient. The Input pin of the
4066 switch can go directly to IC-401, Pin 17, and the Output pin
of the 4066 to IC-401, Pin 15. Pin 15 here is the saae point as
the high sides of C-411 and R-411 if either of these would be sore
convenient.

2. BC-400/560: Pins 14 and 16 are the pertinent pins, with 16
not used. The control pin of the 4066 switch should go to the
CPU, IC-281, Mute pin 26, or either side of R-217, whichever is
most convenient. The Input pin of the 4066 switch can go directly
to IC-1, Pin 16, and the Output pin of the 4066 to IC-1, Pin 14.
Pin 14 here is the saae point as the high sides of C-23 and R-24
if either of these would be acre convenient.

3. BC-768/958 and Regency R-1680; Pins 14 and 16 are the
pertinent pins, with 16 not used. The control pin of the 4066
switch should go to the CPU, IC-14, Mute pin 2, or to the anode of
D-15, whichever is aost convenient. The Input pin of the 4066
switch can go directly to IC-2, Pin 16, and the Output pin of the
4066 to IC-2, Pin 14. Pin 14 here is the saae point as the
junction of R-39 & R-48 or the high side of R-5E if any of these
would be sore convenient.

EDITOR’S NOTE: if you want to try this Squelch S« itch hod to a
scanner not listed above, I'll be glad to identify all the
necessary chips, pin aui bers and connection points for you if
you'll send »e a clean, clear, cotplete copy of the Service Manual
for that scanner. Sorry, but if no aanual, no can help.

I perforaed the above tod to ty PRO-2004 after the ' Professor '
hounded and goaded te into it. The results are subtle, but quite
effective. All the above Realistic scanners Mill profit fro i this
sitple, but capable tod. I can't vouch yet for the Bearcats and
other scanners, but your input Mill be appreciated so I can pass
it along to others. Rom see the Data Sheet and short article
about the RFM-Osc-Mixer-IF-Detodulator chip that is used in so
tany scanners and other Fh radios: hat, CB, conercial, and hone.
This chip is Morth getting to kn om because m hat can be done to one
of these chips can be done to tost ! IBC

MEMORY UPGRADES FOR THE
BC-590XLT. BC-760/950XLT & REGENCY R-1600

I was poring over the scheaatic diagraa of the BC-760/950XLT the
other day when I noticed that the static random access aeaory chip
is identical, pin for pin, in function to the aeaory chips used in
the PRO-2804/5/6, the PRQ-34 and the PRG-2022. How wonderful for
you Bearcat fanatics! Your BC-760/950XLT (or Regency R-1608!
coses stock with a paltry 100 channels, but it's virtually certain
that you can add another 1,508 by following the general guidelines
for HDDs 16, 19 and 37 in #y Scanner Modification Handbooks . 1
have not perforaed this sod to a Bearcat yet, but I was talking to
a fellow recently who said that he has done it to the BC-768/958
and also to the BC-590XLT. Stands to reason since the aeaory
chips appear to be compatible with those in the Realistic scanners
where huge aeaory upgrades are old hat now. Hy exaaination of
several service aanuals and conversations with others now strongly
suggests that at least the above scanners can be upgraded to
16-tines the stock aeaory by the very saae techniques we used for
MODs 16, 19 Si 37. You'll end up with sixteen Blocks of 108

channels each! You could live with that, now couldn't you? The
technique for this is simply resoving the stock sesory chip and
replacing it with a larger 32k x 8 SRAM, typically the Hitachi
HM62256LP-12 or equivalent. The stock aeaory chip has 24 pins and
our new one has 28 pins, so it will not fit onto the ori
pads. No probles; just build your new sesory chip into a snail
perf board; aount it soaewhere nearby and wire its pins to the
original pads in accordance with the instructions and diagraas
given in MODs 16, 19 6 37. In fact, you will build your Extended
Heaory Board exactly like that pictured on page '.31 in Vol-1 of ay-
book. Hiring to the stock aeaory chip's pads will be exactly as
pictured, as well! Feeling bold? Go for the gusto then!

MEMORY UPGRADES FOR THE PRO-2021 AND PRO-32

While we're on the subject of aeaory upgrades, it occurred to ae
to aention that ay MODs 16, 19 & 37 are directly applicable to the
PRO-2021 and the PRO-32, if you're so inclined and happen to feel
that 208-channels are not enough. If you want to perfora the

aeaory upgrade to either of these scanners, just read the general
instructions for MODs 16, 19 6 37 in ay books, and follow the

diagraa on page 131 in Vol-1. You'll end up with 3,200 channels
organized into 16 Blocks of 200-channels each. No sweat!

MEMORY UPGRADES FOR OTHER SCANNERS ?

In the case of the BC-200/205XLT and the Regency R-4030, I’a
afraid you’re "stuck" with 200 channels. Seeas that the UC-1147
CPU has the necessary large chunk of aeaory on board and we don't
dare diddle around with that. There is no external aeaory chi
this unit for us to hack, cut and chop into aega-aeaory.

The foregoing is also true for the BC-560/400XLT. Mesory appears
to be jaaaed on board the CPU where we can't liberate any sore.
Other exaaples in this category are the PRO-2024 and PRO-31

It aay or aay not be possible to puap up the aeaory of other

scanners, but what's the use? Most ten and twenty channel
scanners have their aeaories right on board the CPU where we can't
oonkey around, or in cases where there is an external memory chip,
the CPU will still address only 10 or 20 channels at a time, so
the aost you'd cose up with is saybe 160-328 channels scattered
cut over sixteen individually addressable Blocks. This is
unwieldy and a poor return for the investaent of labor, time and
money. In general, it is best to hack the aeaories only in
scanners with 50 or sore stock channels, and then only if the
mesory chip is an external static RAM. Unfortunately, even soae
of these don't lend themsel ves to sesory expansion including the
PRO-2083, PRO-2002 and PRO-2020.

I don't have the Service Manuals in my files to evaluate all the
current crop of scanners on the sarket, but if your scanner is not
mentioned in this memory article, and if you are determined to get
some sore sesory out of it, send me a clean, clear, coaplete copy
of the Service Manual for that scanner. I'll evaluate it for
sight can be done. Sorry, but if no aanual, no can help. If
want or need a service manual for your scanner, refer to V1N2P6
(Feb, 1991, page 6! for the sources. There's no excuse to not
have the technical manual for your scanner unless it's a boat
anchor out of the past.

THE HORLD SCAHHER REPORT ' (cl 1991

V1H4 - Page 4

NEW ACCESSORY FOR
UNIDEN BC-200/205XLT & BC-100XLT

METROWESrS P-120 RECHARGER FOR PRO PACK 1200

ol-2 of my Scanner Modification Handbook , I wrote about the
new NetroNest PRO PACK 1200 heavy duty NiCad battery pack for the
Uniden BC-200/205XLT and BC-100XLT Handheld scanners. The PRO
PACK 1230 literally doubles the operation time of these scanners
between recharges and it looks exactly like the standard battery
pack. I tested the PRO PACK 1200 under different conditions and
determined that it did everything it was supposed to do, equal to
or better than NetroNest 's specifications. Not bad!

NetroNest has now introduced the P-123, a special charging stand
for the PRO PACK 1230, and do I ever mean SPECIAL! This one is
really slick from appearances right into the nitty gritty of how
it works and what it does! First, the looks:

The P-120 Recharger vaguely resembles a professional two-way
handheld charger, but frankly, I've not seen any pro rigs that
look this good! Finished in crinkle black, the P-120 is built
with soae solid engineering for the physics of gravity! It is
bottoa heavy to give stability; a sloped cradle allows the scanner
to solidly rest for recharging and still allow the operator full
access to the front panel controls. A 110 VAC power cord
unobtrusively enters the rear of the P-120; and there are two
buttons and an LED on the lower front panel. The appearances and
operating controls of the P-120 are pleasant and simple, but what
a powerhouse in operation!

b». ically, the P-120 Recharger has three functions: (1) to
provide a quick, full recharge of the PRO PACK 1280, in five hours
or less; (2) To provide a safe trickle charge after full recharge
to maintain the PRO PACK 1200 at peak power for use at any time;
and (3) to deep discharge the PRO PACK 1200 periodically to
prevent a "memory" effect froa developing in the NiCad batteries.

Embedded into all three functions is a aicroprocessor that keeps
track of what the battery pack needs at any given tiae. Your PRO
PACK 1200 will never be overcharged or undercharged by the P-120!
Operation is simple, and largely hands-off. Just drop the scanner
into the P-120 stand and if the main power switch is ON, the
aicroprocessor will take a look at things and iaaediateiy provide
full recharge current if needed; or if not, then a trickle charge.
When recharging at the full rate the LED flashes green at a rate
of about three flashes per second. When the battery pack becomes
fully charged, the aicroprocessor shuts things down to a trickle
and the LED will glow a steady green.

Other than the ON/OFF switch, the only other operator control is
the second button for DEEP DISCHARGE. Nhen it is pushed, charging
is suspended and the battery pack is allowed to discharge at a
rate of about 200-®a for approximately six hours. Nhen the
battery pack is discharging, the LED glows a steady red. After
tb* oack has been discharged to a deep, but safe level, the aicro-
f jssor turns off the DISCHARGE cycle and immediately starts a
full recharge. About five hours later, the P-120 will auto-cycle
back to trickle charge. That's it; nothing could be simpler!

As long as the P-120 is left turned ON, the scanner can be dropped
into or removed from the stand at any time. The microprocessor
senses any charge requirements and makes the correct decision at
all times. The only absolute operator requirements are to turn
the P-120 ON and to press the DEEP DISCHARGE button, if and when
desired. Everything eise is automatic.

! did something to ay P-120 Recharger that you should NOT do to
yours: disassembled it for a curious look inside. NON! Nothing
hokey or low rent under the covers, either! A very professional
appearing printed circuit board was loaded to the gills with three
integrated circuits, two transistors, two relays, three diodes,
transformer, +5v regulator, a hefty handful of resistors and
capacitors. There are only two things inside that might interest
the hobbyist: a trimmer potentiometer for adjustment of the exact
DEEP DISCHARGE point and a 1-amp fuse that’s not likely to ever
blow. Hobbyists are always interested in things that can be
tweaked, but the trim pot is already factory adjusted to the
exact, precise point, and does not deserve further attention. The
fuse can be replaced if necessary, but if it blows once, the
replacement will probably blow, too. So to preserve the excellent
warranty, it's best to stay out of the innards of the P-120.

Some readers don't want to hear all about the good sides of a
product; they demand to be exposed to the "seamy" side as well.
Ok, I found only one bad thing about the P-120: it's designed
solely and strictly for the PRO PACK 1230 heavy duty battery pack.
You can't recharge standard *AA“ or other NiCad cells with the
P-120 or, if you do, trouble may settle about your head and
shoulders. NetroNest offers other rechargers, though, so the bad
side of the P-120 is only a restriction. Nhat doesn't have 'em?

Since this is a “hacker's newsletter", I suppose that you die-hard
hackers might as well know that the P-120 will recharge six cells
of the oversice "AA“ class provided that the rating is 1200 ma/H.
I'm talking about the rather uncommon NiCad cell that's the same
length as the standard "AA" but about l / B " larger in diameter. I
don't remember what they're called right off, but if your hacker's
battery pack uses six of them in series, the P-120 is probably the
ticket for you. Just write off any warranties if the P-120 is
used for anything but the PRO PACK 1230.

NetroNest offers a double guarantee on the P-120: (1) satisfaction
for 30-days or money back; and (2) 1-year guarantee against defect
with standard caveats and disclaimers. Contact NetroNest for
their catalog or other information as follows: 322 N. Spring;
LaGrange Park, IL 60525; (708! 354-2124.

NEW DISCOVERY ABOUT NiCAD CELLS ?

This little tidbit is offered more to entice some authoritative
information froa you readers than to offer information. I
recently read an article in a trade magazine, maybe the "NASA
Technical Journal", about a discovery pertaining to NiCad cells.
Seems that NASA commissioned Gates and one other manufacturer of
NiCad cells to perform independent studies on the well known
"memory” effects of partially charged and discharged cells.
Apparently, NASA was concerned about longevity and power density

(please turn to page 3)

7 HE Mid SCANNER REPORT • (c) 1991

lflN4 - Page 5

MOTOROLA

SEMICONDUCTOR w—mamm

technical data

Sfm/tArt TO Cf’fifiS Vs&i>

Widen i Keens/Jof sc f WTfe/is

LOW POWER NARROWBAND FM IF

. . . includes oscillator, mixer, limiting amplifier, AFC, quadrature
discriminator, op/amp, squelch, scan control, and mute switch.
The MC3359 is designed to detect narrowband FM signals using
a 455 kHz ceramic filter for use in FM dual conversion commu-
nications equipment. The MC3359 is similar to the MC3357 except
that the MC3359 has an additional limiting IF stage, an AFC output,
and an opposite polarity Broadcast Detector. The MC3359 also
requires fewer external parts.

• Low Drain Current: 3.6 mA (Typ) f® Vqq ~ 6.0 Vdc

• Excellent Sensitivity: Input Limiting Voltage —

- 3.0 dB = 2.0 M V (Typ)

• Low Number of External Parts Required

FIGURE 1 — TYPICAL APPLICATION IN A SCANNER RECEIVER

Toko _£
Type *T
RMC-2A6597HM

f 1 Volume 001

0 002 .F^; 10 k*-

X X out

MC3359

HIGH GAIN
LOW POWER
FM IF

SILICON MONOLITHIC
INTEGRATED CIRCUIT

P SUFFIX

PLASTIC PACKAGE
CASE 707-02

DW SUFFIX

PLASTIC PACKAGE 20
CASE 751D-03

♦

Quadrature

Input

12 l— Demod
I Output

SPectAL. Z.O-M vetstoAj

For soRFfice Aiou*r

MOTOROLA

SEMICONDUCTOR hmhhmh

TECHNICAL DATA

S/mitA/t -To Amp om&t

PJF/Ti CH-ifi5 /A/ /?FAUSr/C Scmj/J&ZS

LOW POWER NARROW BAND FM IF

. . includes Oscillator. Mixer, Limiting Amplifier, Quadrature
Discriminator. Active Filter, Squelch, Scan Control, and Mute
Switch. The MC3357 is designed for use in FM dual conversion
communications equipment.

• Low Drain Current (3.0 mA (Typ) @ Vqq = 6.0 Vdc)

• Excellent Sensitivity: Input Limiting Voltage —

(-3.0 dB) = 5.0 pV (Typ)

• Low Number of External Parts Required

FIGURE 1 — FUNCTIONAL BLOCK DIAGRAM

MC3357

LOW POWffl
FM IF

SILICON MONOLITHIC
INTEGRATED CIRCUIT

P SUFFIX

PLASTIC PACKAGE
CASE 648-06

D SUFFIX

PLASTIC PACKAGE
CASE 751B-03
SO-16

PIN CONNECTIONS

Decoupling [6]

"THE WORLD SCANNER REPORT" (c) 199x

V1N4 - Page 6

THE SUPPLEMENTARY PAGE!

i/e will occasionin'/ include an extra page or two like this one
uhicii Mill he called a 'Suppleaentary Page". There's never an
extra charge for it, and it's one May Me can express our thanks to
for bearing Mith us in this early stage of 'NORLD SCANNER
REPORT'S ' printing history. Thank you!

DISCUSSION OF THE NFH CHIP COMMON TO HOST SCANNERS

'Professor Peabody's" article this month centers around an
integrated circuit that's used in aost every scanner on the aarket
nowadays and in a lot of other radios which have narrow band FH.
The coaplete and proper naae of this chip is... are you ready:

NFH-Osc-Hixer-Liaiter-!!iscriainator-Filter-Squelch-Scan-Hute

Bosh, what a aouthful! For the sake of simplicity, bear with ae
as I subsequently refer to it as simply the “NFH chip". There are
a nuaber of versions of the NFM chip, but all do practically the
saae thing. These chips coae in 16, IS and 20 pin configurations,
and all have virtually the saae functions. We will disregard the
ainor differences froa one variety to the next because they're not
iaportant. What is important is that an NFM chip is used in every
scanner on the aarket today. We aay as well understand the logic
and functioning of this chip because soae of our past, present and
future aodifications will be done to or around it. You should
know what to look for and be able to recognize it where ever it
resides in your scanner. Various versions of the NFM chip are
listed in ‘Professor Peabody's" article in the Table on page 3. A
’ er of popular scanners with the chips’ circuit symbols and
p-. w numbers are also given in that Table.

The NFM chip is practically an entire receiver on a chip, lacking
only a front end RF amplifier, and an audio power aaplifier in the
simplest concept. This very chip and only a handful of other
parts can be asseabled into a full fledged, operable FM receiver,
which is actually done in soae of the very cheap import rigs. For
the most part, though, the NFM chip is only a saall cog on a large
wheel in our scanners. Without it, your scanner could very well
be twice it's present size 3t three tiaes the cost!

On page 6, I have reprinted two Motorola Data Sheets for three of
the most coaaon versions of the NFM chip, and the three shown
there will cover the actual chip used in aost all scanners today.
Referring to the Table on page 3, the coaaon TK-10423 used in the
PRO-2S04/5/6 is actually the saae thing as the HC-3357 on page 6.
The TK-10421M-2 used in the BC-200/205XLT is the saae thing as the
23-pin version of the NC-3359. The NJH-3359D-A as used in aost
other Uniden Bearcat scanners is typified by the 18-pin version of
the MC-3359. And the MC-3361 (not shown) is pretty such the saae
as the MC-3357. So regardless of which scanner you have, just
find and count the pins on your NFM chip, and one of the two Data
Sheets on page 6 will be an exact or very close aatch.

N^ is a technical description of how the NFM chip works in the
2004/5/6 scanners, but if you have a different scanner, don't
despair; it will work the saae way as I describe for the PRO-2B0x;
only the pin nuabers will change, and you can keep track of that
by referring to the appropriate Data Sheet for your NFM chip.

TECHNICAL DISCUSSION OF THE NFH CHIP

A 2nd I.F. signal of 10.7 MHz is injected into pin 16 where it is
fed to the NFH chip's internal Mixer. An external crystal at
19.245 MHz drives Pins 1 & 2, the oscillator, the signal of which
is also fed to the internal Mixer. The subtractive component of
the Mixer signal, 455 KHz (10.700 MHz - 10.245 MHz = 455' KHz) is
fed out of the chip via pin 3 to an external bandpass filter,
soaetiaes known as the I.F. filter. It is this filter which sets
the ultimate selectivity of the receiver's NFM and AM sections.
(Ne Mill Mork Mith this 45 5 KHz I.F. filter in coning nods, so
take note/) The output of the I.F. filter is fed back into the
NFM chip at pin 5 to a very high gain Liaiter Aaplifier where weak
and strong signals alike are amplified to aaxiaua and clipped of
all residual AM signal and noise leaving only an FM signal. The
Liaiter then drives the internal Discriainator (detector! which is
balanced by an external tuning coil at pin 8. The output of the
Discriainator feeds an internal audio preamplifier and outputs
weak audio to pin 9. The audio is routed out to the audio section
of the receiver for further processing and amplification, but a
portion of it is sampled at pin 9 and passed through an external
filter network and then back into the NFM chip at pin 10 where the
sampled audio is further filtered and stripped of extraneous noise
and then outputted to pin 11 for input to an external Noise
Detector. The Noise Detector cospares the raw signal fros pin 11
with the signal froa pin 9 and if they are the saae (no RF signals
cosing in), it does nothing. If the signals are different, then
voice or data are present, and a logic signal is sent back into
pin 12 to operate the internal Squelch generator. A Squelch Logic
signal coses out of the Squelch generator at pin 13 and on to the
scanner’s CPU to tell it whether to "Scan* or "Lock up". When the
scanner is "scanning", an internal electronic switch shunts pin 14
to pin 15 where there is an external ground. This ground "autes"
or silences the receiver when signals are not present. Hhen
signals are present, the ground is internally switched off of pin
14 to allow the receiver to reproduce the audio. Thus, "aute“ and
“Squelch" are not the saae thing, although they work together.

The highlights of the NFH chip are the 455 KHz I.F. output at pin
3; filtered 455 KHz input to pin 5; discriainator tuner at pin 8;
low levei audio output at pin 9; Squelch generation/detection at
pins 18, 11, & 12; Squelch logic output at pin 13 (low or high)
for the CPU; and Mute generation at pin 14. Take note of this:
m hen SQUELCH is set ; the output at pin 13 Mill be Iom at about $
volts ; Mhen the SQUELCH breaks (signals in), the output at pin 13
Mill be high at +4 to + 8 volts, depending on the scanner. He will
use this Squelch Logic for several of our aodifications. Nlso
note this: Mhen SQUELCH is set, the Hute signal at pin 14 Mill be
Iom at about i volts; Mhen SQUELCH breaks, Hute pin 14 goes high
to around +4 to +0 volts. Ne Mill use this ‘Hute Logic' in soae
of our aodifications, starting Mith 'Professor Peabody's' Squelch
SMitch in this issue/

And so you see, the NFH chip is a aost iaportant one. It contains
the equivalent of m hat Mould have been an entire circuit board of
a few years ago. Now, it and its supporting external circuitry
occupy a space of aay be two square inches or so. Acquaint
yourself Mith the specific version of this chip that's used in
your scanner. The best starting point before reaoving the case of
your scanner is the Service Hanual for your unit.

THE HORLD SCANNER REPORT' (c) 1991 HN4 - Suppleaent Page 9

PERSONALLY SIGNED BY THE AUTHOR!
(Autographed copies
available nowhere else!)

'I'

*

H

25

W

s

w

co

(— i

H

&

W

>

Q

<

*

Volume 1 of the Scanner Modification Handbook proved that the average hobbyist could easily
perform some relatively simple changes in the equipment and emerge from the experience with a
greatly enhanced scanner. The step-by-step instructions and photos left no questions unanswered
and even totally non-technical people found that they could restore functions that had been
locked out at the factory, or add anywhere from 1DD to 6,000 more memory channels to popular
scanners such as the Radio Shack Realistic PR0-2004, PR0-2005, PR0-2006, PRO-34 and others.

Now, in Volume 2, modification master Bill Cheek brings you more great enhancements for the
PR0-2004; PR0-2005, PR0-2006, PRO-34, PRO-2022 and Uniden Bearcats BC-100XLT; BC-200/205XLT; and
BC-760/950XLT. He shows how to adapt many of these modifications to other scanners as well. In
Volume 2, you *11 get new circuits and simpler but more effective approaches to adding signal
strength meters, adjusting the scan delay time (0-12 sec), speeding up scan & search rates,
decoding and using CTCSS tones, adding more memory channels, adding an event counter, shielding
plastic cased equipment, reducing interference, restoring locked out bands, adding center tuning
meters, and more. Vol-2 also contains updates to the modifications that appeared in Vol-1 , plus
more tips, hints, explanations, and tricks of the trade to make scanners more useful and
versatile.

Learn how to realign your PR0-2004/5/6 scanner; how to use a VCR to record the action from your
scanner; how to diagnose and repair some scanner problems; how to use Computer BBS ! s to improve
your scanning knowledge. Find out about buying a used scanner; about collecting scanners; how to
get a big boost in the audio output of your scanner; how to build a bench power supply and lots
more. It f s all there in Volume 2 of the Scanner Modification Handbook. You ! ll even learn about
dealing with those new trunked 800 MHz systems that seem so difficult to monitor.

There are plenty of photos and the text is written so that the average hobbyist can follow the
clear step-by-step instructions. And, you don't need exotic test equipment or extra special
tools to do these modifications. Scanner owners will find Vol-2 to be a valuable and constantly
useful reference in many ways. A few modifications suggest that the user be familiar with the
information in Vol-1 first.

The Scanner Modification Handbooks are now available from the author with his autograph and a
personal salutation, if desired, for $17.95 ea plus $3.00 shipping & handling. (Canada, $4.00
S&H; other foreign, $5.00 S & H. Add sufficient extra funds for air mail if desired.) Order
from and make remittance payable to:

COMMTRONI GS ENGINEERING
PO Box 262478-B San Diego, California USA 92196-2478

THE WORLD SCANNER REPORT" (c) 199 x V1N4 - Supplement Page 10

S&UGlCH SWITCH Modwcatjoa/

n/ots : r*j PRO-20^

|?-I 46 /'s €A%'n-y
CUPP&P'

IAJ PRO- Zoo ^ , IT P**/

Be r<?

p,u /</ of ^

Sou>£A. tu>o t*j//tes

A-S SHC&tJ
TO TH& CUT
£a}T)S> Cut ' th/S .

RtS"S/StOA L£AT>
AS SAOLuf/

Add tujo

LoiAeS

\/6 A/PM CHIP

P PO -zoo-4 — XC-z. r/r/DVzo
APO -ZOOS' - -CC- Z. TA/D4ZD

SfaE 1 ** ^

4/5"

OPT/DU /tL
5au£LCH /viod-^

/0OK-2/MK

ne/wi p°t~

LeAv/£ our IP
D6Si #££>• AJor
Aj(£C£-SSAfty

Pftiws uvr

leA mnc l tt66 op CD-HOkPo
,e* /°K Resisra*
f £». /ao/r Rss/stoa

Ml SC /Aatf/C D/ 5
/^/ic 8oARt>

aS/

p-eo -zeop/s

&rf*

// ^
j¥)i)T£.

SCA*/^<

(SAOONV)

hlor£ ••.

^ TO epo

)/!/ As fiouovst

P/tO-1004 - TC3

/>/*) a OK !3

0< Ca/-SM. 0

g^ A y/ujixe r/*)o

PRO -ZOOS'

ZC3

Pth) H 0 /z 13

OP .

CM3 f /f} /z

iSLU)Cd (^>P€

erneR scaaajrrS

See Te* f

Pi us

to, a, 12- ** e

aJoT oset>

• THE NORLD SCANNER REPORT ' (c) Ml
CONFIDENTIAL SUBSCRIPTION ORDER: Please print clearly 1 V1N4

NAME:

STREET:

CITY:

STATE:

ZIP:

PHONE: (

!

AMT ENCLOSED: $_

THE BELON 0JEST1M M OPTIONAL BUT HILL HELP US HELP YOB!

RADIO INTERESTS? (Put YEARS OF EXPERIENCE in each block that applies)
VHF-UHF Aaateur CB Shortwave Professional

Scanning? Radio? Radio? Listening? Radio?

Career/Profession

0* ^'cupation:

L. . the aake l aodel of your scanners and other radio equipment:

List the lake k aodel of any computer equipaent you own/operate:

V1N4 - P age 7

03/24/91 SUBSCRIPTION RATES i ORDER BLANK V1N4

Check Iteas
Desired

PAYABLE IN US FUNDS ONLY

DOMESTIC RATES; (CANADA +1BI ) OTHER F0REI6N

Single copy, per issue $4.00
1991 (4 «os,Jan-June) $15.00
1991 (1 yr) Jan-Dec $25.00
1991-92 (2 yrs) $45.00

$4 surf /$5 Air
$17 surf /$22 Air
$30 surf /$3B Air
$55 surf/$70 Air

Other Available Literature

SCANNER NOD HNDBK, Vol-1: $17.95 + $3.00 S&H*

SCANNER NOD HNDBK, Vol-2: $17.95 + $3.00 SiH*

‘(Canada $4 S&H; Other Foreign $5 SIH; Air Hail extra)

HAKE REMITTANCE PAYABLE IN US FUNDS TO: COHHTRONICS ENSINEERINE
Use the below space to tell us anything else you want!

Enclose a Hi S.A.S.E. and one loose extra staip if you
teed other intonation or a personal reply/

'JHE m£ SCANNER REPORT (c)

of NiCad cells on lengthy space missions where full recharges
sight be few and far between. The conclusion of these studies
failed to disclose any evidence of a "memory effect" I Partially
charged and discharged cells accepted full charge, even after
lengthy periods. This goes against the grain of the “old wives'
tale" that if NiCad cells are not fully discharged followed by an
issediate full recharge, a “seaory effect* will disinish the
cell’s capability. The "cure" was to fully discharge and recharge
it several times to erase the “aesory effect". The studies failed
to show this effect. The report went on to confirm that heat and
over-charging were the greatest single factors that could dasage a
NiCad cell. ! cannot reaeaber where I read this article now and
would like to hear froa any readers who aay have knowledge of this
new finding. By the way, belief in this “old wives' tale" does
not detract fros anyone's credibility since engineers around the
world and even NASA apparently subscribed to the NiCad “sesory
effect". For whatever it is worth, 1 did, too, and even thought I
had seen proof that it existed. Goes to show ya

MORE ABOUT NiCAD BATTERIES

The NiCad battery is among the least understood subjects ir.
electronics. While the physics and chemistry of nickel-cadmium
cells can be rather "hairy", there are some basic facts about them
that can be readily understood and applied, even by the casual
hobbyist. The main idea of a NiCad is to get maximum power for
the least cost. The one-time, up front cost of a NiCad cell is
rather high, compared to an alkaline or carbon zinc cell, but
after a few recharges, it's paid for and the rest of the cell's
life is basically free. That life can be quite long, depending on
how they're used and maintained. Properly fed and nourished, a
NiCad cell is good for hundreds or even thousands of recharges!

There are three important factors on which to focus for maximum
cell life: maximum charging voltage; maximum charge current and
temperature. First, forget the "1.2v“ that's imprinted on every
NiCad cell. That's only a nominal value. The maximum full charge
of a NiCad cell is 1.44 volts, period. If the terminal voltage is
higher than that, it's overcharged and its life is shortened. If
the voltage is under 1.4 volts, then it's not fully charged. The
first rule of thumb, allowing for a bit of measurement error is to

1991 - Pa at 8

never allow a NiCad cell to reach more than 1.40 volts. Along

with this rule is that at 1.8 volt, the cell is considered to be
fully discharged. Hence, the median 1.2 volt label usually found
on the body of the cell somewhere.

Next rule to remember is the maximum charge current of the cell.
First, you have to know the milliampere/hour fma/h) rating of the
cell. The "AA" cell is typically rated at 600 ma/h, !C), which
means that it is capable of generating 608 milliamps for one hour
while maintaining its specified voltage range, 1.4 to 1 volt. The
maximum fast charge current is generally specified to be l l 3 of
the cell's (0 rating, (206-sa for the “AA" cell!, but even at
this maximum, excess heat can be generated within the cell which
can shorted the its life. The recommended trickle charge current
is about l /i • the ma/h rating, or about 66-ma for the typical "AA"
cell. These charge current limits are referred to as the C/3 and
C/10 ratings, respectively. To safely and fully charge a cell,
the current must be greater than C/10 and less than C/3.

Last but not least, the temperature of the cell is of vital
importance. I really don't know the absolute temp limit for NiCad
cells, and it probably varies from one type to another, but if the

cell feels warm to the touch, it is too hot and its life is being

shortened. There are three ways a NiCad cell can get too warm:
(1! too high of a discharge current; (2! too high of a charge
current; and (3! operation in too warm of an environment. Words

to the wise: Keep 'em cool.

Host NiCad rechargers can be checked: first, let a cell or

battery pack charge up fully, say for 14 hours or longer, and

measure the pack's terminal voltage. The measured voltage siiu«d
not exceed 1.40-1.44 volts times the number of cells in the pack.
A 6-cell NiCad pack should not measure more than 8.40 to 8.60
volts when fully recharged. If more or less than that range, the
recharger is defective or not properly designed for the pack.
Next, start with a discharged pack, and insert a milliammeter in
series with one of the two leads between the recharger and the
pack. The charge current should be greater than one-tenth and
less than one-third the ma/h rating of the pack. Then, after the
pack is fully recharged, the trickle charge should be pretty dose
to one-tenth the ma/h rating of the pack. More later; 73/BC

COMMTRONICS ENGINEERING
"THE WORLD SCANNER REPORT"
PO BOX 262478
SAN DIEGO , CA 92196-2478

V 1N4
910326

FIRST CLASS HAIL

“tot’